Drivo Requiring “Full-Coverage Insurance”. Can I get it outside of Drivo for cheaper somehow?

Hello, I’m an American citizen who does not currently own a car and neither do I have any sort of auto insurance. Sometimes I book rental cars with Expedia for short trips within the U.S.A. Most of the time I book with Drivo Rent-A-Car in New Jersey. In the past I’ve purchased the collision damage protection from Expedia, but found that I still needed to purchase additional insurance from Drivo at the counter, as they require proof of “full coverage insurance”. I am a student and would like to save as much money as possible, so my question is: Is there a way to purchase either part or all of this “full coverage insurance” OUTSIDE of Drivo? Is there a chance it could cost less to do this? (And thus, is it worth it to buy Expedia collision damage then?) Perhaps someone knows how I could go about finding this information. Thank you all in advance.